Biophysical principles of brain oscillations and their meaning for information processing

Cosyne 2016. Snowbird, Utah.

Feb 29th, March 1st, 2016

Organizers: Costas Anastassiou, Gabriel Kreiman and Stephanie Jones

Oscillatory activities such as theta (~4-8 Hz), alpha (~7-14Hz), beta (~12-30 Hz) or gamma (~30-80 Hz) have been hypothesized to coordinate neural functioning within and across brain areas. Flexible cooperation among local and distant cell assemblies is thought to underlie the efficacy of cortical performance and, as such, is an essential ingredient of cognition. What are the underlying neural mechanisms supporting such oscillations and how do these mechanisms dictate characteristics of rhythmic activity? How do rhythms manifest in terms of recorded signals and associated time series? How are the rhythms correlated with behavior and are they causally important? More specifically, oscillations are typically monitored via extracellular voltage (Ve) recordings (either from an individual location or from multiple locations). Understanding the link between sub-cellular, cellular and circuit dynamics giving rise to Ve-signals expressing such oscillations is paramount towards understanding how the biophysics underlying rhythms ultimately impact behavior. In this workshop we seek to address how the brain elicits oscillations at the cellular and circuit level, how these mechanisms translate to recorded signals, and how such oscillations give rise to high-level functioning.
This topic is very timely as in the last decade or so new technologies such as high-density silicon probes and 2-photon imaging have allowed concurrent monitoring of hundreds or even thousands of neurons in living and behaving animals. As such, we have entered an era where mechanisms of communication within and across brain areas can be interrogated at their cellular level – oscillations and rhythmic activity are a primary candidate for obtaining such network communication. Based on the aforementioned our goal is to organize a workshop bringing together worldwide experts to discuss the origin and function of oscillations given the newest findings and technologies. To the best of our knowledge, there has been no COSYNE-workshop in the past dealing with this subject and, thus, we expect a large audience. Furthermore, we strived to invite speakers of different backgrounds (theoretical, computational and experimental) whose research interests cover a range of scales (micro, meso and macro) and levels of description (bottom-up, top-down, etc.) We firmly believe that this workshop will be an important contribution and of interest to participants of a range of backgrounds interested to find out about brain oscillations and associated signals but also mechanisms of communication useful to the brain, in general.

SCHEDULE

Monday February 29th

Breakfast: 7-8 AM. The Cliff Ballroom

Biophysics and computational models of neural rhythms

Session Chair: Costas Anastassiou

8:00-8:40

William Stanley Anderson

Modeling Techniques for Studies of Brain Oscillations

8:40-9:20

Gaute Einevoll

What can the local field potential (LFP) tell us about the cortical network activity?

Until now the analysis of population signals like LFP, MEG or MEG has mainly been purely statistical, i.e., based on correlating the measured signal with stimuli or behaviour. However, biophysical forward modeling of these signals from precise network models offers a new path for gaining deeper insights into their neural origin. In the talk I will discuss how such modeling now allows us to distinguish between different candidate neural network models suggested to underlie the observed signals.

Here, we present a novel experimental approach to show that dendritic calcium spikes are clearly detectable in EEG signals. We show that some oscillatory states involved more dendritic calcium than others. The results challenge the assumption that synaptic inputs dominate the EEG.

Spike 'replay' during gamma rhythms in models of wake and NREM sleep: A role for GABA(B) receptor-mediated synaptic plasticity

This presentation will demonstrate and in vitro model of adaptation to repeated ascending input (‘sensory’ stimulation) to neocortex. We will show that two, lamina-specific forms of synaptic plasticity combine to refine the cortical representation, leading to optimised temporal precision and minimised local cortical output at low (30-50 Hz) gamma frequencies. In contrast, replay of prior ‘sensory’ stimulation during a model of NREM sleep was seen at high (50-80 Hz) gamma frequencies. Underlying mechanisms and potential consequences will be discussed.

5:50 - 6:10

Coffee Break

6:10-6:50

Daniel Gibson

Brief Beta Bursts Abounding in Behaving Brains

Original analyses of the statistical distribution of durations of beta bursts in cortex and striatum of behaving monkeys will be presented, along with a review of historical reports of the phenomenon of brief oscillatory bursts. I will conclude with some thoughts on possible functional roles of brief bursts of oscillation.

Complex behaviors like eye-hand coordination are mediated by interactions between systems of saccade and reach brain areas, including area LIP and the PRR, respectively. The synchronization of spiking activity with the local field potential may serve as a mechanism by which the timing of neural events across brain regions can coordinate behavior. We found that spiking activity in the PRR was synchronized to the phase of beta-band activity both in the PRR and area LIP and correlated with both the behavioral suppression of saccade reaction times and the suppression of spiking activity in area LIP. Beta-band synchrony may be a mechanism that controls the timing of neural activity across saccade and reach systems as well as the timing of eye and hand movements.

10:20-11:00

Gabriel Kreiman

Neural rhythms underlying interactions during flexlible rule learning

Rapid adaptation in behavioral choices is critical to our daily endeavors and constitutes a hallmark of dynamic reasoning. Learning new visuomotor mappings led to the emergence of specific responses that associated visual signals with the correct motor output. After learning, those mapping selective signals in the gamma band during the delay period showed dynamic interactions with purely visual and motor responses. These observations provide initial steps towards elucidating the dynamic circuits underlying flexible behavior and how communication across areas leads to rapid learning of task-relevant choices.

Causal roles of neural rhythms

Session Chair: Gabriel Kreiman

4:30-5:10

Laura Colgin

Spatial sequence coding differs during slow and fast gamma rhythms in the hippocampus